Crankshaft Position/Engine Speed Sensor

Sensor is attached to torque converter drive plate housing. Sensor detects drive plate teeth as they pass during engine operation. Sensor provides ECU with engine speed and crankshaft angle position.

The drive plate has 3 large trigger notches 120 degrees apart. There are 20 small teeth between each trigger notch. Each large trigger notch is located 12 small teeth before Top Dead Center (TDC) of each corresponding pair of pistons.

When a small tooth and notch pass under magnet in the sensor, concentration and collapse of magnetic flux induces a small voltage spike into sensor pick-up coil winding. These small voltage spikes enable the ECU to count the teeth as they pass sensor.

When a large trigger tooth and notch pass under sensor, there is a longer than usual delay between voltage spikes. The longer delay tells the ECU a piston will be at TDC position 12 teeth later. According to sensor inputs, the ECU can advance or retard ignition timing as necessary.